\documentclass[12pt]{article}
 \textheight30cm \textwidth14cm \parindent0mm \parskip 1ex plus2ex minus0.8ex
 \voffset -3cm
\begin{document}

For details on \LaTeX\ look at~\cite{lam, goo} (English)
and~\cite{kop.anf, kop.fort} (German).
\begin{thebibliography}{99}
 \bibitem{lam} Leslie Lamport. {\sl\LaTeX\ --- A Document Preparation System}.
               Addison-Wesley Co., Inc., Reading, MA, 1985
 \bibitem{goo} Michel Goossens, Frank Mittelbach, Alexander Samarin. 
               {\sl The \LaTeX\ Companion}. Addison-Wesley Co., Inc., Reading, MA, 1994
 \bibitem{kop.anf} Helmut Kopka. {\sl\LaTeX\ Band~1 --- Einf\"uhrung}.
                   Addison-Wesley, Bonn, M\"unchen, Reading~(Mass.), 1994
 \bibitem{kop.fort} Helmut Kopka. {\sl\LaTeX\ Band~2 --- Erg\"anzungen}.
                    Addison-Wesley, Bonn, M\"unchen, Reading~(Mass.), 1994
\end{thebibliography}

\bigskip
Once more: for details on \LaTeX\ look at~\cite{la, go} (English)
and~\cite{ko.anf, ko.fort} (German).
\begin{thebibliography}{99}
 \bibitem[Lamp85]{la} Leslie Lamport. {\sl\LaTeX\ --- A Document Preparation 
                      System}. Addison-Wesley Co., Inc., Reading, MA, 1985
 \bibitem[Goos94]{go} Michel Goossens, Frank Mittelbach, Alexander Samarin. 
               {\sl The \LaTeX\ Companion}. Addison-Wesley Co., Inc., Reading, MA, 1994
 \bibitem[Kopk94a]{ko.anf} Helmut Kopka. {\sl\LaTeX\ Band~1 --- Einf\"uhrung}.
                           Addison-Wesley, Bonn, M\"unchen, Reading~(Mass.), 1994
 \bibitem[Kopk94b]{ko.fort} Helmut Kopka. {\sl\LaTeX\ Band~2 --- Erg\"anzungen}.
                            Addison-Wesley, Bonn, M\"unchen, Reading~(Mass.), 1994
\end{thebibliography}

\bigskip
And once more: for details on \LaTeX\ look at~\cite{l, g} (English)
and~\cite{k.anf}, \cite[part I,II]{k.fort} (German).
\begin{thebibliography}{99}
 \bibitem[Lamp85]{l} Leslie Lamport. {\sl\LaTeX\ --- A Document Preparation 
                      System}. Addison-Wesley Co., Inc., Reading, MA, 1985
 \bibitem[Goos94]{g} Michel Goossens, Frank Mittelbach, Alexander Samarin. 
               {\sl The \LaTeX\ Companion}. Addison-Wesley Co., Inc., Reading, MA, 1994
 \bibitem[Kopk94a]{k.anf} Helmut Kopka. {\sl\LaTeX\ Band~1 --- Einf\"uhrung}.
                           Addison-Wesley, Bonn, M\"unchen, Reading~(Mass.), 1994
 \bibitem[Kopk94b]{k.fort} Helmut Kopka. {\sl\LaTeX\ Band~2 --- Erg\"anzungen}.
                            Addison-Wesley, Bonn, M\"unchen, Reading~(Mass.), 1994
\end{thebibliography}

\end{document}
